Coriamyrtin synthesis

Due to the more complex structures of most sesquiterpene picrotoxanes compared with the dendrobines, fewer syntheses have been reported. Their structures with up to nine stereogenic centers were too complex to be used as test molecules for newly developed reactions. Three of the syntheses reported beginning with 1979 followed new strategies (two picrotoxinin syntheses and one coriamyrtin synthesis). The other syntheses of picrotoxinin (1), picrotin (2), coriamyrtin (9), tutin (11), corianin (21), methyl picrotoxate (42), and asteromurin A (22) were extensions either of successful dendrobine syntheses or partial syntheses. Remarkably, with one exception, all the syntheses are EPC-syntheses. 

An intermediate of the coriamyrtin synthesis 119) was chosen to synthesize a further main picrotoxane sesquiterpene of Coriaria species, (+)-tutin (11). 

The first synthesis of racemic coriamyrtin (9) was presented by Inubushi et al. 128, 129, 205, 206). To achieve this aim, the authors developed a new protocol for the preparation of highly substituted cis-hydrindanones. 

Allylic bromides 383 and 384 were the relais substances for the synthesis of coriamyrtin (9) (Scheme 43). The allylic bromides were eliminated with potassium ferf-butoxide in toluene affording diene 387. 1,4-Addition with W-bromosuccini-mide in polar solvent at room temperature yielded the unsaturated a-bromo-5-hydroxy unit of 388, which formed the unsaturated epoxide 389 by base treatment. Epoxidation with peracid occurred as expected from the convex face. The cyclic ether moiety of bisepoxide 390 was oxidized to the lactone 368 with ruthenium... 

Corey EJ, Pearce HL (1979) Total Synthesis of Picrotoxinin. J Am Chem Soc 101 5842 Niwa H, Wakamatsu K, Hida T, Niiyama K, Kigoshi H, Yamada M, Nagase H, Suzuki M, Yamada K (1984) Stereocontrolled Total Synthesis of (—)-Picrotoxinin and (-i)-Coriamyrtin via a Common Isotwistane Intermediate. J Am Chem Soc 106 4547 Miyashita M, Suzuki T, Yoshikoshi A (1989) Selective Total Synthesis of (—)-Picrotoxinin and (—)-Picrotin. J Am Chem Soc 111 3728... 

Tanaka K, Uchiyama F, Sakamoto K, Inubushi Y (1982) Stereocontrolled Total Synthesis of ( )-Coriamyrtin. J Am Chem Soc 104 4965... 

Tanaka K, Uchiyama F, Dceda T, Inubushi Y (1983) Synthetic Studies on a Picrotoxane Sesquiterpene, Coriamyrtin. II. An Effective Stereocontrolled Synthesis of the Picrotoxane Skeleton Except for a Ci Unit at the Cg Position and Functionalization of the Five-membered Ring. Chem Pharm Bull 31 1958... 

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